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UV Region (uv + region)
Selected AbstractsGrowth of YCOB single crystals by flux technique and their characterizationCRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2008R. Arun Kumar Abstract Nonlinear optical single crystals of YCOB with good optical quality were grown by the flux technique for the first time. Polycrystalline YCOB samples were synthesized by solid state reaction method. The thermal analysis of the sample was performed with lithium carbonate flux in different weight proportions and the growth temperature was optimised. Single crystals of YCOB with dimensions 3 × 3 × 5 mm3 were obtained by the method of ,slow-cooling'. The grown crystals were characterized by XRD, UV-VIS-NIR, EDAX, FTIR and etching studies. The powder XRD pattern revealed the formation of YCOB compound. The lattice parameters were identified through single crystal XRD studies. The UV-VIS-NIR results showed that the crystal has a sharp cutoff at 220 nm and is nearly 55% transparent over a wide wavelength range enabling applications in the UV region. The EDAX measurement revealed the ,flux-free' crystal formation. The presence of the functional groups belonging to the YCOB crystals was identified by the FTIR results. ,Hillock-like' patterns are observed in the etching studies. The primary emphasis in this study is laid to describe ,flux technique' as an alternative method to grow YCOB crystals. The results are presented and discussed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Simultaneous determination of Zr(IV) and Hf(IV) by CE using precolumn complexation with a [PW11O39]7, ligandELECTROPHORESIS, Issue 10 2007Sadayuki Himeno Professor Abstract A CE method was developed for the simultaneous determination of Zr(IV) and Hf(IV) at trace levels. A lacunary Keggin-type [PW11O39]7, ligand reacted quantitatively with a mixture of trace amounts of Zr(IV) and Hf(IV) to form the so-called ternary Keggin-type anions [P(ZrIVW11)O40]5, and [P(HfIVW11)O40]5, in 0.010,M monochloroacetate buffer (pH,2.2). Since both ternary anions possessed different electrophoretic mobilities and high molar absorptivities in the UV region, Zr(IV) and Hf(IV) were determined simultaneously with direct UV detection at 258,nm. Each peak height was linearly dependent on the concentration of Zr(IV) or Hf(IV) in the range of 5.0×10,7,1.0×10,5,M; a detection limit of 2×10,7,M was achieved. The utility of the proposed CE method was demonstrated for the simultaneous determination of Zr(IV) and Hf(IV) in natural water samples with satisfactory results. [source] Highly Efficient Visible-Light-Induced Photocleavage of DNA by a Ruthenium-Substituted Fluorinated PorphyrinEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2009Michelle Cunningham Abstract A new porphyrin, meso -5-(pentafluorophenyl)-10,15,20-tris(4-pyridyl)porphyrin, has been synthesized. Coordination of two [Ru(bipy)2Cl]+ moieties (where bipy = 2,2,-bipyridine) to the pyridyl nitrogen atoms in the 10,15-positions gives the target complex. Electronic transitions associated with the ruthenium,porphyrin include an intense Soret band and four less intense Q-bands in the visible region of the spectrum. An intense ,,,* transition in the UV region associated with the bipyridyl groups and a metal-to-ligand charge-transfer (MLCT) band appearing as a shoulder to the Soret band are also observed. Electrochemical properties associated with the complex include a redox couple in the cathodic region with E1/2 = ,0.84 V vs. Ag/AgCl attributed to the porphyrin and a redox couple in the anodic region at E1/2 = 0.79 V vs. Ag/AgCl due to the RuIII/II couple. DNA titrations and ethidium bromide displacement experiments indicate the ruthenium porphyrin interacts with DNA potentially through a partial intercalation mechanism. Irradiation of aqueous solutions of the ruthenated complex and supercoiled DNA at a 100:1 base pair/complex ratio with visible light above 400 nm indicates that the complex causes double-strand breaks of the DNA.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Surface-enhanced Raman spectroscopy with ultraviolet excitationJOURNAL OF RAMAN SPECTROSCOPY, Issue 6-7 2005Xu-Feng Lin Abstract Surface-enhanced Raman scattering (SERS) spectroscopy excited with a UV laser was successfully developed and the UV,SER spectra of various adsorbates, including pyridine and SCN,, on different transition metal electrodes were obtained. The experimental requirements for obtaining UV,SERS in an electrochemical system are given. The surface enhancement factor of a roughened Rh electrode covered with thiocyanate as a model molecule was estimated to be about two orders of magnitude in the UV region, consistent with our preliminary theoretical calculation based on the electromagnetic model. The investigation of SERS in the UV region will improve the understanding of the SERS enhancement mechanism and broaden the research field of SERS in areas such as surface science and the life sciences. Copyright © 2005 John Wiley & Sons, Ltd. [source] Nitridation and reoxidation of high- k metal oxide thin films using argon excimer sourcesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2006J. J. Yu Abstract We report for the first time the nitridation and reoxidation of metal oxide films with the active nitrogen and oxygen species produced by argon excimer sources. Preliminary results on 9 nm Ta2O5 films using this method exhibited excellent electrical properties with the leakage current density being up to 3 orders of magnitude lower than the as-deposited films. Breakdown fields were found to be greater than 13 MV/cm. Accumulation capacitance with the nitrided film increased by 25% compared with the as-deposited film. Optical transmittance was as high as 99% in the visible region and more than 74% in the UV region. The refractive index at 632.8 nm was high up to 2.2. The Ar excimer source emitted energetic VUV photons which could break nitrogen triple bonds to produce active nitrogen species and photodissociate O2 to form strong oxidant O3 and highly reactive O (1S) atoms, leading to the nitridation and reoxidation of Ta2O5 without the need for the use of H2O, NH3 and high temperature substrate heating. The nitridation process for a specific film thickness can be optimised by adjusting the VUV irradiation time to achieve increased accumulation capacitance and improved leakage property simultaneously. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] PIN diamond detector development for LYRA, the solar VUV radiometer on board PROBA IIPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2004A. BenMoussa Abstract LYRA (the LYman-alpha RAdiometer onboard PROBA-2) will use diamond detectors for the first time in space solar physics. A set of measurement campaigns was designed to obtain the EUV-to-VIS characterization of the diamond detectors and knowledge of their modes of operation. The outputs of this campaign provide the reference data needed for the optimization of the detectors, and for the LYRA channels definition. The measurements of responsivity in EUV and VUV spectral ranges have been carried out by the Physkalisch-Technische Bundesanstalt (PTB) in Germany at the electron storage ring BESSY II. The detectors spectral responsivity measurements R(,) was done for the following wavelength ranges: 40 to 80 nm, 80 to 120 nm and 120 to 240 nm. The longer wavelength range from 210 nm to 827 nm was measured with the monochromatic light by using a Xe-lamp at IMO-IMOMEC. The diodes exhibit high photoresponse in the deep UV region and over five orders of magnitude in discrimination between deep UV (200 nm) and visible light (550 nm). (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Thermoluminescence and other optical studies on RbBr:Tb3+ crystalsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2007P. K. Manimozhi Abstract Optical absorption, photoluminescence, photostimulated luminescence (PSL) and thermoluminescence (TL) studies on RbBr:Tb3+ crystals irradiated with X-rays is reported. The optical absorption in the UV region confirms the presence of terbium in the host matrix in the trivalent state. Photoluminescence of these crystals exhibits characteristic Tb3+ emissions due to transitions from the 5D3 and 5D4 levels to various levels of the 7F septet. On F-bleaching X-irradiated crystals Z3 centers are observed. The TL glow curve indicates a two-step thermal annihilation process for the radiatively created defects. The presence of the characteristic emissions due to terbium ions in the photostimulation at the F band confirms the participation of Tb ions in the defect-production process. Trap parameters for the TL process are calculated and presented. Emissions under the TL glow peaks contain the characteristic emissions of Tb3+ in addition to the emission due to the recombination of the F electron with V-type centers. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Large enhancement of GaN-UV light emission using silver mirror resonatorPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2006N. M. Ahmed Abstract In this paper we used new microcavity resonator design of extracting light with high efficiency from a high index material (GaN), n > 2 for use in light emitting diode (LED) and laser diode (LD). A GaN/sapphire structure as an active layer was sandwiched between two silver mirrors. For the study two types of microcavity were fabricated: (air/GaN/sapphire/silver) and (silver/GaN/sapphire/silver). Via photo-luminescence measurements we observed 2-fold intensity enhancement in the UV region (364 nm) at room temperature by using 400 nm silver back mirror compared with uncoated sample. The amplitude of the photoluminescence is enhanced 10-times when we used 400 nm back coated together with 50 nm silver as front mirror. Further, a tremendous enhancement was obtained when a small hole was made in the front mirror with 50 nm thickness. The large increment of GaN/sapphire light emission in this microcavity could be caused by few important factors: increasing absorption in the cavity, optical field enhancement due to the resonator and coupling of plasmon in the metallic layer with the UV light. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Improved optical properties using self-organized GaN nanotip structurePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003H. Yamaji Abstract A self-organized GaN nanotip structure, which was a nanoscale tip-shaped pillar, was fabricated on a GaN surface by reactive ion etching (RIE) using chlorine plasma. The nanotip structure with periods smaller than the wavelength of light can provide antireflection and enhanced transmission effects from the ultraviolet (UV) to the visible region (300 nm , 900 nm). We have found that the height and the density of the nanotip structure can be controlled from 0.1 ,m to 2.0 ,m and from 109 cm,2 to 1011 cm,2 by changing etching conditions, respectively. The nanotip structure with controlled height and density exhibited the drastic improvement of the transmission property in the UV region compared with what is conventionally fabricated. These excellent optical properties of the nanotip structure are expected to improve the performances of light-emitting and photo-detective devices. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Microspectrophotometric Analysis of Intact Chromatophores of the Japanese Medaka, Oryzias latipesPIGMENT CELL & MELANOMA RESEARCH, Issue 2 2000TINA N. ARMSTRONG To investigate the possible photoprotective role of chromatophores in fish, the absorbances of four types of intact chromatophores in adult and larval Japanese medaka were analyzed using microspectrophotometric techniques. The absorbance spectrum of each chromatophore class was obtained from 300 to 550 nm. The absorbance spectra of intact leucophores, melanophores and xanthophores were very similar to the published absorbance spectra of the isolated pure pigments contained in each chromatophore type, pteridines, melanin and carotenoids or pteridines, respectively. Based on these absorbance spectra, leucophores and melanophores should provide the most ultraviolet (UV) photoprotection to fish since the compounds they contain, pteridines and melanin, correspondingly, have strong absorbances in the UV region of the spectrum. Xanthophores containing carotenoids are not likely to provide much protection to fish from UV-induced damage since carotenoids have low absorbances in the UV range. Xanthophores containing colored pteridines, however, may provide somewhat greater UV protection to fish, since pteridines absorb more light than carotenoids in the UV portion of the spectrum. The relative frequency, coverage and thickness of these two types of xanthophores should determine how much protection xanthophores as a chromatophore type would provide against UV-induced damage. [source] The bactericidal effect of ultraviolet and visible light on Escherichia coliBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2008Natasha Vermeulen Abstract The bactericidal radiation dosages at specific wavelengths in the ultraviolet (UV),visible spectrum are not well documented. Such information is important for the development of new monochromatic bactericidal devices to be operated at different wavelengths. In this study, radiation dosages required to cause mortality of an Escherichia coli strain, ATCC 25922, at various wavelengths between 250 and 532 nm in the UV and visible spectrum were determined. Radiation at 265 nm in the UV region was most efficient in killing the E. coli cells and 100% mortality was achieved at a dose of 1.17 log mJ/cm2. In the visible spectrum, the radiation dosages required for a one-log reduction of the E. coli cell density at 458 and 488 nm were 5.5 and 6.9 log mJ/cm2, respectively. However, at 515 and 532 nm, significant killing was not observed at radiation dosage up to 7 log mJ/cm2. Based on the cell survival data at various radiation dosages between 250 and 488 nm, a predictive equation for the survival of E. coli cells is derived, namely log(S/S0),=, ,(1.089,×,107 e,0.0633,)D. The symbols, S0, S, ,, and D, represent initial cell density, cell density after irradiation, wavelength of the radiation and radiation dosage, respectively. The proportion of the surviving E. coli cells decreases exponentially with the increase in radiation dosage at a given wavelength. In addition, the radiation dose required for killing a certain fraction of the E. coli cells increases exponentially as the wavelength of radiation increases. Bioeng. 2008;99: 550,556. © 2007 Wiley Periodicals, Inc. [source] A new method for fibrous protein analysis illustrated by application to tubulin microtubule polymerisation and depolymerisation,CHIRALITY, Issue 9 2006Rachel Marrington Abstract A thermostatted micro volume Couette cell has been designed to enable linear dichroism (LD) data to be collected at a range of temperatures. The cell is a development of the traditional Couette flow LD cell and includes the recent development of micro-volume LD (20,40 ,L) coupled with the addition of a heating element, temperature probe and controller. This new micro volume Couette LD cell opens the way not only to the LD analysis of systems where sample volume is critical, but also for the LD analysis of temperature sensitive samples. The polymerization of the microtubule protein tubulin has been followed in a range of different conditions using the thermostatted micro volume Couette LD cell. The focusing lenses on the cell, which are required for the microvolume cell, have the side benefit of significantly reducing the light-scattering artifacts caused by the large size of tubulin microtubules. It is now possible to monitor real-time polymerization and depolymerization kinetics, and any structural rearrangements of chromophores within the polymer. In the case of tubulin, the LD spectra revealed a greater change in the orientation of tryptophan residues at ,290 nm during polymerization compared to other contributing chromophores,guanine, phenylalanine, and tyrosine. The improvements in instrumental design have also allowed LD spectra of tubulin to be collected down to ,230 nm (previous data have only been available from the near UV region), which means that some indication of protein backbone-orientation changes are now available. It was observed during this work that apparent LD intensity maxima are in fact artifacts when the high-tension voltage is high. The onset of such artifacts has been observed at much lower voltages with light-scattering fibrous proteins (including tubulin) than with nonscattering samples. Therefore, caution must be used when interpreting LD data collected with medium to high photomultiplier tube voltages. Chirality, 2006. © 2006 Wiley-Liss, Inc. [source] | ||||||||||||||||